PROJECT SUMMARY The average duration of cold-storage for deceased-donor kidneys in the U.S. can range from ~9 to >30 hrs in the U.S. depending on geographic location. It is well established that the longer a kidney is stored cold prior to transplant, the greater the likelihood of post-transplant complications like delayed graft function. This is particularly true for organs from aging donors or donors with co-morbidities?an ever-expanding proportion of the U.S. donor pool?which display increased sensitivity to injury during cold storage. Little is known about the mechanisms that determine the rate and extent of cold-storage injury in human organs. This lack of knowledge presents a critical barrier to the development of therapeutic strategies to reduce the clinical impact of cold-storage injury. We have recently discovered that cold storage induces human kidneys to produce fibrinogen within renal tubular cells. Upon restoration of normothermia/normoxia, fibrinogen is secreted into the vasculature where it can aggregate erythrocytes in a rouleaux formation leading to pathologic plugging of microvessels. We hypothesize that renal fibrinogen is a major effector of cold-storage injury and therefore represents a viable target to improve organ resilience after cold storage. Ex Vivo Organ Perfusion (EVOP) has emerged as a research and clinical platform providing an opportunity to directly test this hypothesis in a translationally relevant setting. Here, we will exclusively use human tissues to achieve two objectives: 1) Determine the mechanism by which cold- storage induces renal fibrinogen synthesis; and 2) Evaluate EVOP as a therapeutic platform to ameliorate fibrinogen-mediated pathology pre-transplant. Successful completion of these objectives will establish a new paradigm for prevention of cold-storage-induced organ injury with the potential to save patient lives by improving both access to organs and post-transplant outcomes.